(1) Field of the Invention
The present invention relates to a focus out detecting apparatus and an optical disc apparatus using the same.
(2) Description of the Related Art
As a prior art of the present invention, for example, Japanese Patent Application Laid-Open No. 1996-185637 (Patent Document 1) is given. Patent Document 1 discloses “by comparing the level of a focus error signal with a predetermined level of a reference signal, focus out which causes a just-focus on a recording layer different from the one on which data recording or reproducing is being performed is detected”.
Further, as another prior art of the present invention, for example, Japanese Patent Application Laid-Open No. 1996-203108 (Patent Document 2) is given. Patent Document 2 discloses “when focus out occurs, a focus error signal of a relatively high level is generated first, and then reflected light quantity per area is decreased. By paying attention to this, a focus actuator is driven in such a manner that an objective lens is moved apart from a disc surface when detecting that the reflected light quantity per area is less than a second reference value in a predetermined period after detecting a defocus state during focus servo control”.